The broad and long-term objective of this ongoing research program is to elucidate the neuroendocrine control systems which govern reproductive processes in a representative primate, the rhesus monkey. The principal thrust of this investigation is to characterize the hypothalamic pulse generator which governs the circhoral discharges of the gonadotropic hormones congruent to the release of GnRH into the pituitary portal circulation. As a first step, the description of the electrophysiological correlates of pulsatile gonadotropin release and their source(s) will be completed. The modulation of this electrophysiological activity by gonadal hormones and pharmacological agents known to modify gonadotropin secretion will then be studied to determine the possible role of pulse generator activity in the mode of action of these agents. Lastly, the electrophysiological activity of the pulse generator in physiologic as well as pathophysiologic contexts will be investigated using telemetry of signals from chronically implanted hypothalamic recording electrodes. These studies will include the normal menstrual cycle, pregnancy and parturition, the influence of suckling and the advent of puberty. The effects of mild restraint and the introduction of cardiac catheters previously shown to interfere with normal hypophysial-ovarian function will also be examined.